?? test_support.cpp
字號(hào):
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// -
// ************************* -
// HUFFMAN CODING EXAMPLES -
// ************************* -
// -
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// -
// Implementation of random-number generators and chronometer -
// -
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// -
// Version 1.00 - January 24, 2005 -
// -
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// -
// WARNING -
// ========= -
// -
// The only purpose of this program is to demonstrate the basic principles -
// of Huffman codes. It is provided as is, without any express or implied -
// warranty, without even the warranty of fitness for any particular -
// purpose, or that the implementations are correct. -
// -
// Permission to copy and redistribute this code is hereby granted, provided -
// that this warning and copyright notices are not removed or altered. -
// -
// Copyright (c) 2005 by Amir Said (said@ieee.org) & -
// William A. Pearlman (pearlw@ecse.rpi.edu) -
// -
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// - - Inclusion - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
#include <time.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "test_support.h"
#ifdef CLOCKS_PER_SEC
const double ClockRate = 1.0 / CLOCKS_PER_SEC;
#else
const double ClockRate = 1.0e-6;
#endif
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// - - Implementations - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Error(const char * s)
{
fprintf(stderr, "\n\n -> Error: ");
fputs(s, stderr);
fputs("\n Execution terminated!\n", stderr);
exit(1);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Chronometer::start(char * s)
{
if (s != NULL) puts(s);
if (on)
puts("chronometer already on!");
else {
on = true;
mark = double(clock());
}
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Chronometer::restart(char * s)
{
if (s != NULL) puts(s);
time = 0.0;
on = true;
mark = double(clock());
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Chronometer::stop(void)
{
if (on) {
on = false;
time += clock() - mark;
}
else
puts("chronometer already off!");
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
double Chronometer::read(void)
{
return (on ? time + (clock() - mark) : time) * ClockRate;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Chronometer::display(char * s)
{
double sc = (on ? time + (clock() - mark) : time) * ClockRate;
int hr = int(sc / 3600.0); sc -= 3600.0 * hr;
int mn = int(sc / 60.0); sc -= 60.0 * mn;
if (s != NULL) printf(" %s ", s);
if (hr) {
printf("%d hour", hr);
if (hr > 1) printf("s, "); else printf(", ");
}
if ((hr) || (mn)) {
printf("%d minute", mn);
if (mn > 1) printf("s, and "); else printf(", and ");
}
printf("%5.2f seconds.\n", sc);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Random_Generator::set_seed(unsigned seed)
{
s1 = (seed ? seed & 0xFFFFFFFU : 0x147AE11U);
s2 = s1 ^ 0xFFFFF07U;
s3 = s1 ^ 0xF03CD2FU;
};
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
double Random_Bit_Source::set_probability_0(double p0)
{
if ((p0 < MinProbability) || (p0 > 1.0 - MinProbability))
Error("invalid random bit probability");
prob_0 = p0;
threshold = unsigned(prob_0 * double(0xFFFFFFFFU));
ent = ((p0 - 1.0) * log(1.0 - p0) - p0 * log(p0)) / log(2.0);
return ent;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Random_Bit_Source::set_entropy(double entropy)
{
if ((entropy < 0.0001) || (entropy > 1.0))
Error("invalid random bit entropy");
double h = entropy * log(2.0), p = 0.5 * entropy * entropy;
for (int k = 0; k < 8; k++) {
double lp1 = log(1.0 - p), lp2 = lp1 - log(p);
double d = h + lp1 - p * lp2;
if (fabs(d) < 1e-12) break;
p += d / lp2;
}
set_probability_0(p);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Random_Bit_Source::switch_probabilities(void)
{
set_probability_0(1.0 - prob_0);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Random_Bit_Source::shuffle_probabilities(void)
{
if (word() > 0x80000000U) set_probability_0(1.0 - prob_0);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
unsigned Random_Bit_Source::bit(void)
{
return (word() > threshold ? 1 : 0);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Random_Data_Source::Random_Data_Source(void)
{
symbols = 0;
dist = 0;
prob = 0;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Random_Data_Source::~Random_Data_Source(void)
{
delete [] dist;
delete [] prob;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Random_Data_Source::assign_memory(unsigned dim)
{
if (symbols == dim) return;
symbols = dim;
delete [] dist;
delete [] prob;
prob = new double[dim];
dist = new unsigned[dim];
if ((prob == 0) || (dist == 0)) Error("cannot assign random source buffer");
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
double Random_Data_Source::set_distribution(unsigned dim,
const double probability[])
{
assign_memory(dim);
double sum = ent = 0.0;
unsigned s = low_bound[0] = 0;
const double DoubleToWord = 1.0 + double(0xFFFFFFFFU);
for (unsigned n = 0; n < symbols; n++) {
double p = probability[n];
if (p < MinProbability) Error("invalid random source probability");
prob[n] = p;
dist[n] = unsigned(0.49 + DoubleToWord * sum);
unsigned w = (dist[n] >> 24);
while (s < w) low_bound[++s] = n - 1;
sum += p;
ent -= p * log(p);
}
while (s < 256) low_bound[++s] = symbols - 1;
if (fabs(1.0 - sum) > 1e-4) Error("invalid random source distribution");
return ent /= log(2.0);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
double Random_Data_Source::set_tg(double a)
{
double s, r = 0, e = 0, m = symbols;
if (a > 1e-4)
s = (1.0 - exp(-a)) / (1.0 - exp(-a * m));
else
s = (2.0 - a) / (m * (2.0 - a * m));
for (int n = symbols - 1; n >= 0; n--) {
double p = (a * n > 30.0 ? 0 : s * exp(-a * n));
if (p < MinProbability) {
r += MinProbability - p;
p = MinProbability;
}
else
if (r > 0)
if (r <= p - MinProbability) {
p -= r;
r = 0;
}
else {
r -= p - MinProbability;
p = MinProbability;
}
prob[n] = p;
e -= p * log(p);
}
return e / log(2.0);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
double Random_Data_Source::set_truncated_geometric(unsigned dim,
double entropy)
{
assign_memory(dim);
double max_entropy = log(symbols) / log(2.0);
double mgr_prob = (dim - 1) * MinProbability;
double min_entropy = ((mgr_prob - 1.0) * log(1.0 - mgr_prob) -
mgr_prob * log(MinProbability)) * 1.2 / log(2.0);
if ((entropy <= min_entropy) || (entropy > max_entropy))
Error("invalid data source entropy");
// find distribution with desired entropy
Zero_Finder ZF(0, 2);
double a = ZF.set_new_result(max_entropy - entropy);
for (unsigned itr = 0; itr < 20; itr++) {
double ne = set_tg(a) - entropy;
if (fabs(ne) < 1e-5) break;
a = ZF.set_new_result(ne);
}
set_distribution(symbols, prob);
if (fabs(ent - entropy) > 1e-4) Error("cannot set random source entropy");
return ent;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Random_Data_Source::shuffle_probabilities(void)
{
for (unsigned n = symbols - 1; n; n--) {
unsigned m = integer(n + 1);
if (m == n) continue;
double t = prob[m];
prob[m] = prob[n];
prob[n] = t;
}
set_distribution(symbols, prob);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
unsigned Random_Data_Source::data(void)
{
unsigned v = word(), w = v >> 24;
unsigned u = low_bound[w], n = low_bound[w+1] + 1;
while (n > u + 1) {
unsigned m = (u + n) >> 1;
if (dist[m] < v) u = m; else n = m;
}
return u;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Zero_Finder::Zero_Finder(double first_x, double second_x)
{
phase = iter = 0;
x0 = first_x;
x1 = second_x;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
double Zero_Finder::set_new_result(double y)
{
if (++iter > 30) Error("cannot find solution");
if (phase >= 2) {
if (y * y0 <= 0) {
if ((phase == 2) || (fabs(y1) < fabs(y2))) {
x2 = x1;
y2 = y1;
}
x1 = x;
y1 = y;
}
else {
if ((phase == 2) || (fabs(y0) < fabs(y2))) {
x2 = x0;
y2 = y0;
}
x0 = x;
y0 = y;
}
// interpolation y = [(x-x0)-f]/[g(x-x0)+h]
if (fabs(y0) < fabs(y1)) {
double r = y0 / y2, c = x2 - x0;
double s = y0 / y1, d = x1 - x0;
x = x0 - (c * d * (s - r)) / (c * (1.0 - s) - d * (1.0 - r));
}
else {
double r = y1 / y2, c = x2 - x1;
double s = y1 / y0, d = x0 - x1;
x = x1 - (c * d * ( s - r)) / (c * (1.0 - s) - d * (1.0 - r));
}
phase = 3;
return x;
}
if (iter > 8) Error("too many initial tests");
if (phase == 1) {
if (y * y0 <= 0) { // different signs: bracketed interval
y1 = y;
phase = 2;
if (fabs(y0) < fabs(y1)) { // regula falsi interpolation
double s = y0 / y1;
x = x0 - ((x1 - x0) * s) / (1.0 - s);
}
else {
double s = y1 / y0;
x = x1 - ((x0 - x1) * s) / (1.0 - s);
}
}
else { // same sign: increase search interval
x += x1 - x0;
x0 = x1;
y0 = y;
x1 = x;
}
return x;
}
y0 = y;
phase = 1;
return x = x1;
}
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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